The riddle this week on The Riddler was about finding the largest sequence of integers between 1 and 100 such that each integer is only used once and always followed by a multiple or a factor. A basic R code searching at random [and programmed during a massive downpour on Skye] led to a solution of 69:

although there is no certainty this is the best p… And the solutions posted the next week showed sequences with length 77! [Interestingly, both posted solutions have a sequence starting with 87. And they seem to exploit the graph of connections between integers in a much more subtle way that my random exploration of subsequences.]